Bolts or deadbolts are well known devices for locking a door shut for security purposes. In such well-known arrangements, the deadbolt or bolt is mounted in the body of the door and the deadbolt is operated by mechanical operating devices mounted on either side of the door. When the deadbolt is operated to a locked position it typically extends or projects from the side of the door into an opening in the door jam or wall to which the door is mounted. Thus, the deadbolt when operated to an extended position, “bolts” or “locks” the door in a closed position. The mechanical operating devices also can operate to retract the bolt into the side of the door to unlock the deadbolt or bolt.
In typical arrangements, one mechanical device used to operate a deadbolt may be a key cylinder into which a key is inserted. The key then can rotate the cylinder which, in turn, operates the deadbolt through various mechanical linkages. Another mechanical device that may be used to operate a deadbolt includes a knob that can be turned manually that, in turn, operates the deadbolt through various mechanical linkages.
It is known to use a key cylinder and knob device together to operate deadbolts. The key cylinder is normally mounted on the exterior side of the door so that a user can use a unique key to operate and lock the deadbolt from the exterior side of the door. The manual knob is typically mounted on the interior of the door and operates the deadbolt from the interior side of the door without a key. Thus, the user can easily lock and unlock the deadbolt from the interior of the door without using or locating a key.
It is sometimes desirable for users to disable the mechanical device for operating the deadbolt that is mounted on the exterior of the door. This can occur in situations in which the user does not wish to permit a person with a key to operate the deadbolt from the exterior side of the door such as, for example, a landlord/tenant situation in which the tenant does not wish the landlord to enter a rental property. Another important use of this feature is to prevent unauthorized access through the manipulation of the deadbolt by lock “picks” or the like. Mechanisms that disable the operation of a mechanical device used to operate a deadbolt are called “lock-out” devices.
Known lock-out devices for deadbolts are unreliable, difficult and clumsy to use and have safety concerns in that they do not signal to a user when a lock-out mechanism is in operation.